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Abstract

The CuII atom of the title complex, [Cu(C17H15N2S2)2], lies on a twofold rotation axis, and is in a distorted tetra­hedral geometry with the two bidentate N2S2 Schiff bases. In the crystal structure, the mol­ecules are inter­connected into chains along the c axis by weak C—HS inter­molecular inter­actions. The crystal packing is further stabilized by C—Hπ inter­actions.

Acknowledgments

MTHT and MTI thank Rajshahi University for financial support. The authors thank the Malaysian Government and Universiti Sains Malaysia for the Scientific Advancement Grant Allocation (SAGA) grant No. 304/PFIZIK/653003/A118.

supplementary crystallographic
information

Comment

Synthesis (Ali & Tarafder, 1977) and crystal structure (Shanmuga Sundara Raj
et al., 2000) of S-benzyldithiocarbazate (SBDTC) have been
reported. We have been greatly involved in the chemistry of Schiff bases
derived from SBDTC, and also on their metal complexes because of their
interesting physico-chemical properties and potentially useful biological
activities (Ali et al., 2002, 2008; Tarafder et al., 2001,
2002). In continuation of our interests, we report herein the syntheses of the
cinnamaldehyde Schiff base of SBDTC and its copper complex, along with the
x-ray structural analysis of the four-coordinated CuII complex.

The CuII atom of the title complex, lies on a twofold rotation axis and the
asymmetric unit therefore contains one-half of a molecule (Fig. 1). Based on
other thiosemicarbazones (Ali et al., 2002; Tarafder et al.,
2001, 2002), the coordination mode of the CuII complex is as expected, i.e
bis-chelated through the two azomethine nitrogen atoms and the two thiolate
sulfur atoms. The CuII center is in a distorted tetrahedral geometry with
the N2S2 donor atoms of the two Schiff base ligands (Fig. 1). Both
nitrogen atoms (N1 and N1A) and sulfur atoms (S1 and S1A) from the two ligands
are coordinated at opposite positions. The N—Cu—N and S—Cu—S bond
angles are 104.29 (5)° and 134.452 (14)°, respectively, and reflective of the
elongation of the Cu—S bond length [ca 0.19 Å] over the Cu—N bond
length. The Cu1—N1 and Cu1—S1 distances of 2.0663 (10) Å and 2.2648 (3) Å, respectively, are in the same range as those in other four coordination
CuII complexes of the related Schiff base ligands (Ali et al., 2008;
Castiñeiras et al., 1998; Goswami & Eichhorn, 2000). The
CuII-bidentate rings are slightly non-planar. The Cu1—S1—N1A—N2A—C10
ring has a maximum deviation of 0.085 (1) Å for the N1A atom. The mean plane
of the propenyl moiety (C7/C8/C9) makes a dihedral angle of 12.15 (9)° with
mean plane of the attached C1–C6 benzene ring. The dihedral angle between the
C1–C6 and C12–C17 phenyl rings of the two ligands is 8.73 (7)°. Bond lengths
and angles observed in the Schiff base ligand are of normal values (Allen
et al., 1987).

In the crystal packing (Fig. 2), the molecules are interconnected by weak
C—H···S intermolecular interactions (Table 1) into chains along the c
axis. The crystal structure is further stabilized by C—H···π interactions
(Table 2) involving the C1—C6 benzene ring (centroid Cg1).

Experimental

The Schiff base ligand was prepared by adding cinamaldehyde (1.32 g, 10 mmol) to
a hot solution of S-benzyldithiocarbazate (SBDTC) (1.98 g, 10 mmol) in
absolute ethanol (40 ml), as reported previously (Ali & Tarafder, 1977). The
mixture was refluxed for 10 min. The yellow precipitate which formed was
isolated and washed with hot ethanol. The yellow solid product was
recrystallized from absolute ethanol (yield: 1.52 g, 46%). The copper complex
was synthesized by adding the copper nitrate trihydrate (0.31 g, 0.5 mmol) in
ethanol (10 ml) to a hot solution of the above Schiff base ligand (0.31 g, 1 mmol) in ethanol (80 ml) and the reaction mixture was refluxed for 5 min when
a brownish precipitate was formed. The product was separated and washed with
hot ethanol (yield: 0.32 g, 74%). Green single crystals of the title complex
were recrystallized from a chloroform-absolute ethanol (10:3 V/V) solution
after 20 d at room temperature.

Refinement

All H atoms were positioned geometrically and allowed to ride on their parent
atoms, with C—H distances in the range 0.93–0.97 Å. The Uiso
values were constrained to be 1.2Ueq of the carrier atom. The highest
residual density peak is located 0.38 Å from Cu1 and the deepest hole is
located 0.46 Å from S2.

Special details

Experimental. The low-temparture data was collected with the Oxford Cyrosystem Cobra
low-temperature attachment.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger.